Some thoughts on my card choices here:
Cavern of souls: Too powerful an effect not to play when all your creatures are humans. Also not sure I could play Scab Clan without a Cavern in the list.

Scab Clan Berserker: This card has been discussed a lot lately, mostly in reference to the 5C human decks. I will admit that when I first read that thread I thought “hmm that may be interesting in a delver list” and wouldn't ya know it Caleb Durward includes three of them in his VSL delver list. I am not 100% sold on this card yet. Perhaps 2 is just the wrong number, but I have found it to be a bit more high variance then I would like in this list. In testing it has run the gamut from drop on turn 1 deal 10-12 damage before they can plow it amazing all the way to an over-costed chump blocker or discard fodder for Dack. At least one game if it was a snapcaster I could have flashbacked time walk with flusterstorm backup.

Vampiric Tutor: This slot has fluctuated a lot, but (despite the card disadvantage) I feel it gives the list a little extra consistency. Vamp for Time walk, Cavern, an answer post-board, or a counter for late-game protection are all strong plays. Vamping for Ancestral with a delver trigger on the stack to guarantee a flip is also a fun play :)

2 vs 3 Cabal Therapy: Cabal therapy is one of the most challenging, high variance cards to play in vintage. It can be anything from a B Gitaxian Probe that doesn’t cantrip to a devastating mind twist when paired with a Git Probe & Pyromancer. Therapy is essentially the reason to be on Black, but I am not sure if it is good enough.

Some Notable Cuts/Cards I want to have room for:
Snapcaster Mage: I feel like room needs to be made for at least one Snapcaster...could drop a flusterstorm? Cut the Scab-Clan Berserkers completely?

Wasteland: Lots of Decks skimping on Basics these days since Lodestones restriction, but Cavern occupies the slot and 21 lands is to many for Delver.

4th Pyromancer: Again, I am on the fence on Scab-Clan. If its ends up cut, a 4th Pyro is a likely addition.
Dark Confidant: I am a BIG bob guy, but it is just too slow for what the deck is trying to accomplish and Delver does not run Jace or Top to control the life loss.

Demonic Consultation: Vampiric has been more consistent for me, but please convince me otherwise!

Looking for advice/opinions on this list. I feel like Delver has the speed and flexibility to race Mentor and enough disruption to compete with Storm. Delver of Secrets is still a house vs Shops, and although the oath matchup is admittedly terrible, it is not widely played at this time. I had been tinkering with a URg List with Delver, Pyromancer and Mayor of Avarbuck. Making Flipped Delver’s 4/3’s is cool, but ultimately I found it to be a bit greedy.

For me, the primary focus of the deck is consistency, and incremental advantage.

Delver remains a good choice against shops, but I'm still not sold on it in any other matchup. I ended up cutting them because the deck can beat shops without Delver. Against Mentor, I never found Delver to be all that insane. It was good and went over the top, but it still presents a clock that's a bit too slow for my liking.

Cabal Therapy has been what has won me the most games against Mentor. Being able to reduce the number of cards in their hand has, in my experience at least, makes Mentor a much less potent threat. My feeling is the Pyromancer/therapy interaction is what is the strongest pull to these colors, so it makes sense to go all in on it.

I really don't like Scab-Clan Berzerkers in this shell. It has tension with the discard plan, and is much higher on the curve than I like. The way I get ahead with Pyromancer is by being able to Gush very aggressively, and ending my curve at 2 better facilitates this. I also don't like running a Cavern in my Gush deck.

Consultation vs Vamp is close, I like Consultation because it isn't card disadvantage, and I'm generally using it to grab a Pyromancer, Therapy or a Gush. Vamp seems like a better toolbox card, but Consult supports is more the fourth-fifth copy of a bunch of cards.

For the sideboard, I think fighting a resolved Mentor is a fools errand, so the board plan I've been going with is centered around stopping Mentor from resolving.

That's my take on the deck, make of that what you will. I have a personal preference for consistent and focused decks, so take this all with a grain of salt.

@letseeker Is there a tendrils missing from your list? This could be a personal thing but casting yag will with all of those tutors and a fastbond without being able to be like "oops I win" would drive me nuts.

@WashableWater I agree with no Cavern in your list.
How has Jace VP performed for you? I tried them out for a bit and found them to be slower than I liked. To me, the one thing that delver lists have over Mentor lists is that they are inherently faster, and Jace VP purposely slows the game down. Delver wants to force opposing decks to play at their faster pace. Mentor Wants to control the board best they can while sculpting a hand that can drop a mentor and win over the next two turns or sooner.

@p3temangus JVP has been very good for me, but I also think 3 might be too much. The looter mode is ok, being able to dump a therapy then flash it back without black mana is sometimes relevant. I'll tend to lead with a JVP over a Pyromancer because it becomes much easier to get a couple Pyromancer triggers with a Jace in play.

Once flipped, he actually supports Pyro quite well. A lot of the things that prevent you from attacking with a Pyromancer are 2 power. Shrinking a token/snapcaster/revoker/Thalia allows you to be more aggressive, and a 9/11 blightsteel can be less of a threat than a Pyromancer.

Pyromancer decks operate on incremental advantage, which JVP excels at. While flashing back a Recal, DT or Time Walk can win a game on the spot, buying back a Gush/Preordain here and there can pull you pretty far ahead.

I like JVP a lot, I wouldn't run less than 2 in my lists. 3 may be a bit much, but they do pitch to Force.

@p3temangus it changed a lot, i could never deceide on a tendrills, an empty the warrens, or a fourth yp, and with the fourth yp i still had the oops i win because i could chain together so many spells and flood the board, but as i said i never deceided which was best and it does come to personal preference

Hey everyone, I've post a bunch of 3-1 and 4-0 with Grixis Pyromancer on modo a few months back. Lately the deck seems to fail to outrace Mentor. I am still trying different ways in the SB to combat it (Sulfur Elemental, Dread of Night, Sudden shock) But its a difficult matchup. I'm still torn if I like Snapcaster better than JVP. I wish we could play Jace, the Mind Sculptor but its difficult to cast him consistently. I'm still not giving up hope on this deck, but i did retire my Delvers for now :(

Delver has fallen off of the strength ladder due to Eldrazi Shops being super aggro its tough to outrace. Pyromancer is still really good block the Thought-Knots, Smasher is tough with trample but I do like Pyromancer decks vs Shops still. I also think Cabal Therapy is REALLY REALLY good in the format right now as well as Baleful Strix. I'll be testing the deck tomorrow with some friends (they are on Storm and Esper Mentor). Also i'll be probably running in the daily tonight.

@i_b_TRUE Before Shops started including Eldrazi, Delver may have been one of the strongest cards in the matchup. Similar to what you describe, I got BLOWN OUT by a turn 2 Thought-Knot (exiling my bolt) and my delver flipped right away. Bolt + Elemental token to kill Thought-Knot is extremely doable, especially with the bolt replacing the dead token, but the difference between 3 and 4 toughness in this format is like night and day.

I am not ready to move my delvers back to the binder just yet, but if Eldrazi shops continues to gain momentum it will probably have to happen. It even made me consider some number of echoing truth MB, since it can be broken with Cabal Therapy and helps a lot with the Oath matchup.

@p3temangus Young Pyromancer is one of my favorite cards, so I'm doing anything I can to make it keep going!

But the Edlrazi shops is difficult for Delver, and Mentor is a huge annoying problem four Pyromancer decks. The best answer is unfortunately Dread of Night in testing which isn't that great. But it does do some work vs the random White Trash lists running around.

@p3temangus Young Pyromancer is one of my favorite cards, so I'm doing anything I can to make it keep going!

But the Edlrazi shops is difficult for Delver, and Mentor is a huge annoying problem four Pyromancer decks. The best answer is unfortunately Dread of Night in testing which isn't that great. But it does do some work vs the random White Trash lists running around.

". . . the random White Trash lists running around." I wonder when folks are going to wake up and realize that there is nothing "random about these decks. This isn't 2006.
-Storm.

@Stormanimagus I think your taking that the wrong way? When you look at the meta, a deck that really isnt showing up consistently could be considered "random" since you wont be prepared. Those decks do cause issues for the the decks not ready for the tax cards. Dread of Night does some work vs Thalia/Spirits. Is this more clear?